Devices for moulding cast imprints of a section of the inner surface of a tubular member exist. Known devices typically comprise two sealing parts connected by a rod or a shaft. The relative positions of the two sealing parts are fixed by the rod or shaft connecting them, and when the device is inserted inside a tubular member, the two sealing parts seal off a section of the tubular member in which section an imprint of the inner surface thereof are to be moulded. In the following, the sealing part, which is inserted the furthest inside the tubular member is denoted the farthest sealing part, whilst the other sealing part is denoted the closest sealing part.
A moulding mass is injected through a passage in one of the sealing parts or through the connecting rod/shaft and into the confined space between the two sealing parts. Subsequently, the moulding mass is left for some time to cure into a cast containing an imprint of the inner surface of the tubular member.
When the cast has to be removed, it is simply pulled out by drawing the rod/shaft connected to the sealing parts. Since the rod/shaft is connected to the sealing parts, the drawing of the rod/shaft produces a force applied by the farthest sealing part to the cast, which causes the cast to be pushed out by the farthest sealing part. However, since the cast typically is more or less flexible/elastic, the pushing force on the cast and the friction between the cast and the section of the inner surface of the tubular member will cause the cast to compress, thereby tending to increase the diameter thereof. This will increase the risk of damaging the cast imprint of interest and of breaking the connecting rod/shaft, thereby leaving the cast and part of the moulding device inside the tubular member, which will necessitate a time consuming recovery operation.
The above problems are increased, if the tubular member comprises a section with reduced dimensions which should be passed by insertion of the moulding device. The cast would have to be reduced in diameter to pass by the section of the tubular member with reduced dimensions, but drawing the connection rod/shaft provides a compression of the cast and therefore an expansion of its diameter. Naturally, the severity of this problem increases with increased reduction of the dimensions of the tubular member.
EP 0 337 700 A2 describes a moulding device arranged to be inserted inside a tubular member, comprising a shaft (230) having an outlet port (410) and two flanges (250, 260), where the two flanges (250, 260) are arranged to fit tightly inside the tubular member and where the outlet port (410) is placed between the two flanges (250, 260). When a moulding material has been injected and cured to form a cast, the moulding device is removed together with the cast from the inside of the tubular member by pulling the distal end of the shaft, thereby applying a pushing force on the farthest end of the cast, which results in the similar problems of compressing and eventually damaging the cast as described above.
U.S. Pat. No. 2,618,014 discloses a moulding device to be inserted into a tubular structure e.g. in order to detect a defect in said tubular structure. The device comprises a heating housing element (23) for heating a tubular plastic element (25) placed on and fastened to an inflatable expander element (24). Said inflatable expander element (24) is inflated by air pressure. The device further comprises a flexible tube (26) for positioning of elements (23), (24) and (25). A replica of the tubular structure is made by heating the tubular plastic element (25) in the heating housing element (23) and pushing the expander element (24) and tubular plastic element (25) to the area of the tubular structure to be examined. The expander element (24) is expanded using air pressure and thereby the tubular plastic element (25) is forced against the tubular structure to make a replica thereof. After cooling of the tubular plastic element (25), the air pressure is bled from the expander element (24) and the device is removed from the tubular structure using the flexible tube (26). A problem of the presented solution is how to assure the withdrawing of the replica after casting e.g. how to ensure that the replica is not lost in the tube during withdrawal.
U.S. Pat. No. 3,966,871 discloses a method and apparatus for inspection of tubular cavities e.g. in a pressurized-water reactor steam generator. The apparatus comprises an inlet (3) for a moulding mass, a leading dam (2a) comprising a first closing disk (21a) and a trailing dam (2b) comprising a second closing disk (21b). The dams may be inflatable. A tube (4a) serves as an interconnection between leading dam (2a) and trailing dam (2b) and further as an inflation tube for the leading dam (2a). Likewise a tube (4b) may serve as an inflation tube for the trailing dam (2b). The inlet (3) is comprised by the second disk (21b) and an outlet vent (5) is comprised by the first disk (21a). The trailing dam (2b) and the leading dam (2a) together with the tubular cavity define a sealed volume into which moulding mass may be injected. When injected moulding mass injected into a volume defined by the two dams (2a, 2b) has cured into a replica of the tubular cavity, the replica is removed from the tubular cavity by pulling either the inlet (3), which is connected to the leading dam (2a) through (4a), or one of the inflation tubes, (4a) or (4b), the latter being connected to the leading dam (2a) through (4a). The result of pulling the leading dam (2a) is that a pushing force is applied on the farthest end of the cast/replica (leading dam end), which results in the similar problems of compressing and eventually damaging the cast as described above.
FR 2612833 discloses a method and apparatus for making an imprint of an internal thread in a bore, said apparatus comprising a central axis (906) and inflatable water-proof joints (911). A moulding mass (resin) is introduced into a volume defined by the thread (902) and the inflatable joints (911) being in an inflated state. After curing of the moulding mass into a replica of the thread, the inflatable joints (911) are deflated and collapsed towards the central axis (906) with the help of cables (916), thereby detaching the replica from the thread and enabling an extraction of the replica from the bore. A problem of the presented solution is how to assure the withdrawing of the replica after casting e.g. how to ensure that the replica is not lost in the bore during withdrawal.
UK 2,155,390 discloses a method and apparatus for testing tube surfaces, said apparatus comprising a pair of moles (30, 31), a cylindrical plug (13) with a circular cross-section provided with a longitudinal flat surface (14) extending the length of the plug, control cables (26) attached to the plug (13), a moulding mass, wire gaze (22), control cables (27) for the moulding mass, and a loading rod (17). The moles (30, 31) are entered into the tube of which the surfaces are to be tested. The plug (13), entered to the tube using the loading rod (17), is made to rest on the moles (30, 31). Moulding mass is entered into the volume formed by the tube and the longitudinal flat surface (14) of the plug (13). After curing of the moulding mass into a replica of the surface of the tube, the plug is removed using the control cables (26). The replica is removed from the tube by using the control cables (27) connected to the wire gaze (22) embedded into the replica. A problem of the presented solution is how to assure the withdrawing of the replica after casting e.g. how to ensure that the replica is not lost in the tube during withdrawal.